The invention relates to a linear motion device. Such linear motion devices are in particular roller body thread drives and linear roller bearings, such as ball bushes, ball and roller rail guides, and ball splines.
Such linear motion devices are known from the prior art and are widely used in machine tools, for instance. Typically, these devices are provided with inscriptions, such as the type, serial number, precision class, and manufacturing date. Recently, there has been a demand to make such inscriptions computer-readable, so that they can be detected automatically in keeping track of inventory, for instance. For that purpose, bar codes are already in use today.
So-called RFID tags (for radio frequency identification) are also known from the prior art. Such tags can be read out in contactless fashion with the aid of electromagnetic waves. They typically require no energy storing means, since while being read out they are supplied with energy from outside, likewise by means of electromagnetic waves. Compared to bar codes, these tags have the advantage that they can store more data and can also be read out over greater distances and without visual contact. A data processing unit is also often provided in a RFID tag, for instance to protect the stored data with encryption processes to prevent the data from being read out without authorization.
In machine tools, RFID tags in accordance with European Patent Disclosure EP 1 339 014 A1 or European Patent Disclosure EP 0 155 662 A2 are applied to tools, so that the machine controller can take the actual tool dimensions stored in memory in them into account in controlling the tool path. Tags of this kind are sold on the market for instance by the Balluff company, with the designation “Information System BIS C” and are distinguished by a high degree of protection from IP67 in accordance with IEC 60529; that is, the tags are intrinsically especially well protected against the special stresses in a machine tool from cooling lubricants, chips, and so forth, and are therefore relatively expensive.
At the same time, very inexpensive but virtually unprotected RFID tags are also known, for instance from U.S. Pat. No. 6,424,263 B1, and these are soon expected to replace the present price labels for individual products. In these tags, the applicable silicon chip and the antenna associated with it are supported by a plastic film that can be glued from outside onto the product to be identified. The antenna is often applied to the substrate film by a printing process. Moreover, work is already being done on replacing the silicon chip with a circuit comprising organic semiconductors, which can likewise be applied to the substrate film by a printing process. However, if used in a machine tool, such virtually unprotected tags would soon be destroyed.